We present a novel approach to fabricating micro- and nano-particles over a wide range of sizes, extending from 1 mm to sub-100-nm. The technique relies on capillary instabilities in multi-material optical fibers. The typical fiber design incorporates a core made of the target particle material and having size close to the desired particle diameter, while the cladding is a thermoplastic polymer, both co-drawn in the viscous state from a macroscopic preform. Our results demonstrate the efficiency of particle extraction, uniformity of size distribution, as well as the controllability of particle size. This approach allows for the scalable production of micro- and nano-particles for a variety of applications. The major novelty and departure from all other alternatives is that we start the process from a macroscopic preform that is then stretched down to the size required. Thus by structuring this preform at the macroscopic scale, the resulting nano-scale particles may inherit this structure.